Long Lasting Antibodies From Convalescent Pertussis Patients Induce ROS Production and Bacterial Killing by Human Neutrophils

Difference in respiratory syncytial virus-specific Fc-mediated antibody effector functions between children and adults

Respiratory syncytial virus (RSV) infections are a major cause of bronchiolitis and pneumonia in infants and older adults, for which there is no known correlate of protection. Increasing evidence suggests that Fc-mediated antibody effector functions have an important role, but little is known about the development, heterogeneity, and durability of these functional responses. In light of future vaccine strategies, a clear view of the immunological background and differences between various target populations is of crucial importance. In this study, we have assessed both quantitative and qualitative aspects of RSV-specific serum antibodies, including IgG/IgA levels, IgG subclasses, antibody-dependent complement deposition, cellular phagocytosis, and NK cell activation (ADNKA). Samples were collected cross-sectionally in different age groups (11-, 24-, and 46-month-old children, adults, and older adults; n = 31-35 per group) and longitudinally following natural RSV infection in (older) adults (2-36 months post-infection; n = 10). We found that serum of 24-month-old children induces significantly lower ADNKA than the serum of adults (P < 0.01), which is not explained by antibody levels. Furthermore, in (older) adults we observed boosting of antibody levels and functionality at 2-3 months after RSV infection, except for ADNKA. The strongest decrease was subsequently observed within the first 9 months, after which levels remained relatively stable up to three years post-infection. Together, these data provide a comprehensive overview of the functional landscape of RSV-specific serum antibodies in the human population, highlighting that while antibodies reach adult levels already at a young age, ADNKA requires more time to fully develop.

Enhanced glycolysis by ATPIF1 gene inactivation increased the anti-bacterial activities of neutrophils through induction of ROS and lactic acid

ATP synthase inhibitory factor 1 (ATPIF1) is a mitochondrial protein that regulates the activity of FoF1-ATP synthase. Mice lacking ATPIF1 throughout their bodies (Atpif1-/-) exhibit a reduction in the number of neutrophils. However, it remains unclear whether the inactivation of ATPIF1 impairs the antibacterial function of mice, this study aimed to evaluate it using a mouse peritonitis model. Mice were intraperitoneally injected with E. coli to induce peritonitis, and after 24 h, the colonies of E. coli were counted in agarose plates containing mice peritoneal lavage fluids (PLF) or extract from the liver. Neutrophils were analyzed for glucose metabolism in glycolysis following LPS stimulation. Reactive oxygen species (ROS) and lactic acid (LA) levels in neutrophils were measured using flow cytometry and Seahorse analysis, respectively. N-Acetylcysteine (NAC) and 2-Deoxy-d-glucose (2-DG) were employed to assess the role of ROS and LA in neutrophil bactericidal activity. RNA-seq analysis was conducted in neutrophils to investigate potential mechanisms. In ATPIF1-/- neutrophils, bactericidal activity was enhanced, accompanied by increased levels of ROS and LA compared to wildtype neutrophils. The augmented bactericidal activity of ATPIF1-/- neutrophils was reversed by pretreatment with NAC or 2-DG. RNA-seq analysis revealed downregulation of multiple genes involved in glutathione metabolism, pyruvate oxidation, and heme synthesis, along with increased expression of inflammatory and apoptotic genes. This study suggests that the inactivation of the Atpif1 gene enhances glucose metabolism in neutrophils, resulting in increased bactericidal activity mediated by elevated levels of ROS and LA. Inhibiting ATPIF1 may be a potential approach to enhance antibacterial immunity.

Bordetella pertussis targets the basolateral membrane of polarized respiratory epithelial cells, gets internalized, and survives in intracellular locations

The airway epithelial barrier is a continuous highly organized cell layer that separates the exterior from the underlying mucosal tissue, preventing pathogen invasion. Several respiratory pathogens have evolved mechanisms to compromise this barrier, invade and even reside alive within the epithelium. Bordetella pertussis is a persistent pathogen that infects the human airway epithelium, causing whooping cough. Previous studies have shown that B. pertussis survives inside phagocytic and nonphagocytic cells, suggesting that there might be an intracellular stage involved in the bacterial infectious process and/or in the pathogen persistence inside the host. In this study we found evidence that B. pertussis is able to survive inside respiratory epithelial cells. According to our results, this pathogen preferentially attaches near or on top of the tight junctions in polarized human bronchial epithelial cells and disrupts these structures in an adenylate cyclase-dependent manner, exposing their basolateral membrane. We further found that the bacterial internalization is significantly higher in cells exposing this membrane compared with cells only exposing the apical membrane. Once internalized, B. pertussis mainly remains in nondegradative phagosomes with access to nutrients. Taken together, these results point at the respiratory epithelial cells as a potential niche of persistence.

The role of bactericidal and opsonic activity in immunity against Bordetella pertussis

INTRODUCTION

Pertussis vaccines have drastically reduced the disease burden in humans since their implementation. Despite their success, pertussis remains an important global public health challenge. Bordetella pertussis resurgence could be a result of greater surveillance combined with improved diagnosis methods, changes in Bordetella pertussis biology, vaccine schedules, and/or coverage. Additionally, mechanisms of protection conferred by acellular pertussis (aP) and whole-cell pertussis (wP) vaccines differ qualitatively. There are no clear immune correlates of protection for pertussis vaccines. Pertussis antigens can induce toxin neutralizing antibodies, block adherence or engage complement mediated phagocytic/bactericidal killing.

AREAS COVERED

We reviewed the existing evidence on antibody-mediated serum bactericidal and opsonophagocytic activity and discussed the relevance of these functional antibodies in the development of next-generation pertussis vaccines.

EXPERT OPINION

Current paradigm proposes that wP vaccines may confer greater herd protection than aP vaccines due to their enhanced clearance of bacteria from the nasopharynx in animal models. Functional antibodies may contribute to the reduction of nasal colonization, which differentiates aP and wP vaccines. Understanding the intrinsic differences in protective immune responses elicited by each class of vaccines will help to identify biomarkers that can be used as immunological end points in clinical trials.